MKSAP Quiz: Evaluation for an episode of dizziness

MKSAP Answer and Critique

The correct answer is C. Orthostatic presyncope. This content is available to ACP MKSAP subscribers in the Foundations of Clinical Practice and Common Symptoms section. More information about ACP MKSAP is available online.

The most likely diagnosis is orthostatic presyncope (Option C). Patients presenting with dizziness may be grouped into one of four distinct categories: vertigo, presyncope, disequilibrium, or nonspecific dizziness. Presyncope shares pathophysiology with syncope and is caused by transient cerebral hypoperfusion. Symptoms depend on the underlying cause and may include lightheadedness, visual changes (tunnel vision), warmth, nausea, and near loss of consciousness. Patients often report the sensation of “almost blacking out.” Importantly, neurologic symptoms and vertigo do not occur in patients with presyncope. Presyncope is differentiated from syncope by the lack of loss of consciousness or postural tone. The differential diagnosis for presyncope is the same as for syncope; it is commonly associated with medications (i.e., antihypertensives), dehydration, and numerous medical conditions, including diabetes mellitus, which causes small fiber neuropathy and resultant autonomic dysfunction. Evaluation begins with measurement of orthostatic vital signs and an ECG. Further testing, such as with echocardiography or cardiac event monitoring, may be appropriate based on the results of the initial evaluation. This patient presents with a symptom complex consistent with presyncope, characterized by the sensation of nearly passing out while going from a sitting to a standing position. This likely represents orthostatic hypotension, perhaps secondary to his multiple antihypertension medications, and he should undergo measurement of orthostatic vital signs and an ECG.

Benign paroxysmal positional vertigo (BPPV) (Option A) is the most common cause of peripheral vertigo. It presents with recurrent and brief episodes of vertigo triggered by head movement and often accompanied by nausea and imbalance. This patient does not describe vertigo and, although his symptoms had onset with positional changes, the lack of recurrence and absence of vertigo make BPPV very unlikely.

Hypoglycemia (Option B) includes a wide variety of neuroglycopenic and adrenergic symptoms and should be included in the differential diagnosis for patients with both dizziness and loss of consciousness. Although this patient is taking multiple medications that may cause hypoglycemia, the transient nature of his symptoms, spontaneous improvement, and onset with postural changes make hypoglycemia an unlikely cause of his event.

A posterior circulation transient ischemic attack (TIA) or stroke (Option D) is an important diagnostic consideration in patients presenting with dizziness. Symptoms often include vertigo along with neurologic findings such as nystagmus, dysarthria, diplopia, and ataxia. This patient with established cardiovascular disease is at risk for an ischemic event, but he does not describe vertigo or other neurologic symptoms, making TIA an unlikely diagnosis.

Key Points

• Presyncope is characterized by lightheadedness, visual changes (tunnel vision), warmth, nausea, and near loss of consciousness; patients with presyncope do not have vertigo.
• Presyncope is differentiated from syncope by the lack of loss of consciousness or postural tone.